Undermarket

From Flight From Darkness

Aside from the Primary Pumping Station, the most notable location among the not-yet-fully-mapped sprawling corridors and networks of claustrophobic ventilation tunnels that comprises deck 6 of the Tower is a collection of shops away from the public eye. They come out in force when the ship is on alert, since Security is occupied elsewhere, but even when not, this is a good place to find them. This is known to and tolerated by Security, so long as the vendors do not cross certain lines - because some of them inevitably do, and this makes a convenient place to find them when that happens.

Dark-corner peddlers and ventilation-shaft smugglers and thieving technicians or hydroponics workers and pimps and drug dealers and...well, if it is illegal or immoral and someone is selling it on the ship, odds are, it is for sale here. Not that all the shops are exclusively crooked: some legitimate merchants, and many more gray market ones, take advantage of the reputation and corresponding foot traffic, and the less legitimate vendors are all too happy to hide behind them.